In lift trucks of the type contemplated it has been one of the most persistent problems encountered over the years to provide an upright construction which affords the operator of the truck good visibility through the upright. Heretofore various means have been devised for improving, or which may incidentally improve, operator visibility through the telescopic uprights of lift trucks, including upright structures such as are disclosed in U.S. Pat. Nos. 4,030,568, 4,069,932, 4,207,967, 4,356,893, 4,401,191, 4,421,208, 4,432,438, 4,441,585, 4,585,093 and 4,657,471. Other exemplary prior art of general background relevance relative to improving such visibility is disclosed in U.S. Pat. Nos. 4,355,703 and 4,374,550 (common assignee) and in patents and cross-referenced applications (now patents) identified and referenced therein.
Such improvements have included locating the lift cylinders outboard, behind, or in front of the uprights, or locating them interiorly of the upright rails. The latter interior construction is illustrated by U.S. Pat. No. 4,441,585, whereas lift cylinders located outboard of the sides of the upright are illustrated by U.S. Pat. No. 4,030,568. U.S. Pat. Nos. 4,355,703, 4,374,550 and 4,421,208 (all common assignee) disclose a plurality of inventions and embodiments which have in common asymmetric upright constructions in which the lift cylinder or cylinders is (are) located behind and asymmetric to the central plane of the upright. U.S. Pat. No. 4,585,093 (common assignee) discloses yet another lift cylinder arrangement with improved visibility, as do the multi-stage uprights disclosed in U.S. Pat. Nos. 4,401,191 and 4,432,438 (common assignee). All of these latter patents have in common a plurality of novel constructions which remove the visibility obstruction inherent in locating lift cylinders in the center of the mast.
U.S. Pat. No. 4,441,585, on the other hand, locates lift cylinders interiorly of the fixed telescopic rails of the upright sections on opposite sides of the upright, and further, locates the outer webs of fixed upright rails at an angle relative to the webs of adjacent movable upright sections.
U.S. Pat. Nos. 4,069,932 and 4,207,967 locate the upright assembly rearwardly of and forwardly of the forward drive wheels, respectively, and at a transverse spacing between the side rail assemblies which are substantially in line with the front drive wheels, thereby increasing the opening between the side rails and the visibility therethrough.
Other patents of general background relevance are cited in certain of the above-identified patents.